Electrical power systems in industrial plants and commercial infrastructure require structured voltage stepped-down distribution. Understanding the distinct roles of High Tension (HT) switchgear and Low Tension (LT) main panels is critical for electrical design engineers.
1. HT Panels (High Tension: 11kV / 33kV)
HT panels receive raw high-voltage supply directly from the electricity utility grid before transformer step-down:
- Primary Switchgear: Vacuum Circuit Breakers (VCB) or SF6 Gas Insulated Breakers.
- Safety Protection: Overcurrent, Earth Fault, and Differential Protection Relays (Numerical Relays).
- Enclosure & Insulation: Air Insulated Switchgear (AIS) with high creepage distance and safety interlocks.
2. LT Panels (Low Tension: 415V 3-Phase / 230V 1-Phase)
Located on the secondary side of distribution transformers, LT panels distribute power to building loads:
- Main Switchgear: Air Circuit Breakers (ACB) for main incomers and Molded Case Circuit Breakers (MCCB) for outgoing feeders.
- Busbar Sizing: Copper or High-Conductivity Aluminium busbars calculated based on continuous current rating and short-circuit withstand capacity (e.g., 50kA for 1 sec).